IP Multimedia services provide a dynamic combination of voice, video, messaging, data, etc. within the same session. By growing the number of basic applications and the media which it is possible to combine, the number of services offered to the end users will grow, and the inter-personal communication experience will be enriched. This will lead to a new generation of personalised, rich multimedia communication services, including so-called “combinational IP Multimedia” services.
The UMTS (Universal Mobile Telecommunications System) is a third generation wireless system designed to provide higher data rates and enhanced services to users. UMTS is a successor to the Global System for Mobile Communications (GSM), with an important evolutionary step between GSM and UMTS being the General Packet Radio Service (GPRS). GPRS introduces packet switching into the GSM core network and allows direct access to packet data networks (PDNs). This enables high-data rate packets switch transmissions well beyond the 64 kbps limit of ISDN through the GSM call network, which is a necessity for UMTS data transmission rates of up to 2 Mbps. UMTS is standardised by the 3rd Generation Partnership Project (3GPP) which is a conglomeration of regional standards bodies such as the European Telecommunication Standards Institute (ETSI), the Association of Radio Industry Businesses (ARIB) and others. See 3GPP TS 23.002 for more details.
The UMTS architecture includes a subsystem known as the IP Multimedia Subsystem (IMS) for supporting traditional telephony as well as new IP multimedia services (3GPP TS 22.228, TS 23.228, TS 24.229, TS 29.228, TS 29.229, TS 29.328 and TS 29.329 Releases 5 to 7). IMS provides key features to enrich the end-user person-to-person communication experience through the use of standardised IMS Service Enablers, which facilitate new rich person-to-person (client-to-client) communication services as well as person-to-content (client-to-server) services over IP-based networks. The IMS is able to connect to both PSTN/ISDN (Public Switched Telephone Network/Integrated Services Digital Network) as well as the Internet.
The IMS makes use of the Session Initiation Protocol (SIP) to set up and control calls or sessions between user terminals (or terminals and application servers). The Session Description Protocol (SDP), carried by SIP signalling, is used to describe and negotiate the media components of the session. Whilst SIP was created as a user-to-user protocol, IMS allows operators and service providers to control user access to services and to charge users accordingly. The 3GPP has chosen SIP for signalling between a User Equipment (UE) and the IMS as well as between the components within the IMS.
By way of example, FIG. 1 illustrates schematically how the IMS fits into the mobile network architecture in the case of a GPRS/PS access network (IMS can of course operate over other access networks). Call/Session Control Functions (CSCFs) operate as SIP proxies within the IMS. The 3GPP architecture defines three types of CSCFs: the Proxy CSCF (P-CSCF) which is the first point of contact within the IMS for a SIP terminal; the Serving CSCF (S-CSCF) which provides services to the user that the user is subscribed to; and the Interrogating CSCF (I-CSCF) whose role is to identify the correct S-CSCF and to forward to that S-CSCF a request received from a SIP terminal via a P-CSCF.
Within the IMS service network, Application Servers (aSs) are provided for implementing IMS service functionality. Application Servers provide services to end users in an IMS system, and may be connected either as end-points over the 3GPP defined Mr interface, or “linked in” by an S-CSCF over the 3GPP defined ISC interface. In the latter case, Initial Filter Criteria (IFC) are used by an S-CSCF to determine which Applications Servers should be “linked in” during a SIP Session establishment (or indeed for the purpose of any SIP method, session or non-session related). The IFCs are received by the S-CSCF from an HSS during the IMS registration procedure as part of a user's Subscriber Profile.
A precondition for a user to get access to the IMS and its services is that the user has previously been “provisioned” in the network, i.e. that subscriber and related service data has been registered in central databases such as the Home Subscriber Server (HSS) and Subscription Locator Function (SLF). Whenever a network operator wishes to launch a service over an IMS network, the operator is unlikely to know exactly which subscribers will wish to make use of the service. The operator has two options; either pre-provision the whole subscriber base in the IMS network, or implement some form of autoprovisioning method whereby subscribers can be provisioned as and when they subscribe to the service.
WO2007/099090 claims to disclose one such autoprovisioning method. More particularly, the document addresses the problem encountered when a subscriber attempts to register with the IMS when that subscriber is not provisioned in the IMS. At registration, legacy Home Location Register (HLR) subscriber data is extracted using the Radius accounting procedure and stored in the HSS database. The authentication and authorisation procedure is assumed to be performed in the GPRS network prior to accessing IMS. Therefore the received IMS register is assumed to be authentic. At the location query procedure the private ID (IMPI) is fetched and identified by comparing it with the earlier stored IMSI value, where the IPMI may be derived from the IMSI. [The IMSI is stored in GMS/UMTS AuC node and the IMPI in IMS AVG node for authentication purposes.] The available data will be stored in the HSS and the registration procedure will be successful.
A number of problems may arise with the procedure described in WO2007/099090. Firstly, the procedure depends on radius accounting being performed from the GPRS towards the HSS, and other authentication methods cannot be used. Secondly, in a multiple HSS network with a SLF, the SLF will not be provisioned with the HSS location of the subscriber, and the selection of an HSS for the subscriber will be made by the access network. Thirdly, the decision to provision the subscriber in the network is based only on the fact that a subscriber tries to access the network, and as such business aspects are not considered. Fourthly, the only data that can be stored in the HSS is what is received in the access attempt. Finally, the business and charging systems will not be aware of the provisioned subscriber.